[Samsung Galaxy Nexus] breversa:
I tried to reboot to recovery after installing CM, to no avail.

Here's the OpenGapps install log :

# Begin Open GApps Install Log
------------------------------------------------------------------
ROM Android version | 6.0.1
ROM Build ID | cm_maguro-userdebug 6.0.1 MOB30M 777a955073 test-keys
ROM Version increment | 777a955073
ROM SDK version | 23
ROM/Recovery modversion | 13.0-20160706-UNOFFICIAL-maguro
Device Recovery | TWRP 3.0.0-0
Device Name | maguro
Device Model | Galaxy Nexus
Device Type | phone
Device CPU | armeabi-v7a,armeabi
Installer Platform | arm
ROM Platform | arm
Display Density Used | 320
Install Type | Clean[Data Wiped]
Smart ART Pre-ODEX | false
Google Camera already installed | Clean
FaceUnlock Compatible | true
Google Camera Compatible | true
New Camera API Compatible | false[force_api]
Current GApps Version | No GApps Installed
Google Camera version | Legacy
Installing GApps Zipfile | /sdcard/INSTALL/open_gapps-arm-6.0-nano-20160709.zip
Installing GApps Version | 20160709
Installing GApps Type | nano
Config Type |
Using gapps-config | Not Used
Remove Stock/AOSP Browser | false[NO_Chrome]
Remove Stock/AOSP Camera | false[NO_CameraGoogle]
Remove Stock/AOSP Email | false[NO_Gmail]
Remove Stock/AOSP Gallery | false[NO_Photos]
Remove Stock/AOSP Launcher | false[NO_GoogleNow]
Remove Stock/AOSP MMS App | false[NO_Hangouts]
Remove Stock/AOSP Pico TTS | false[default]
Ignore Google Contacts | false
Ignore Google Dialer | false
Ignore Google Keyboard | false
Ignore Google Package Installer | false
Ignore Google NFC Tag | false
Ignore Google WebView | false
[B]Total System Size (KB) | 659152
Used System Space (KB) | 433552
Current Free Space (KB) | 225600
Additional Space Required (KB) | 2528 << See Calculations Below[/B]
------------------------------------------------------------------
# End Open GApps Install Log

INSTALLATION FAILURE: Your device does not have sufficient space available in
the system partition to install this GApps package as currently configured.
You will need to switch to a smaller GApps package or use gapps-config to
reduce the installed size.

!!! WARNING !!! - Duplicate files were found between your ROM and this GApps
package. This is likely due to your ROM's dev including Google proprietary
files in the ROM. The duplicate files are shown in the log portion below.

# Begin GApps <> ROM Duplicate File List
/system/vendor/lib/libfrsdk.so
# End GApps <> ROM Duplicate File List

# Begin GApps Size Calculations
------------------------------------------------------------------
TYPE | DESCRIPTION | SIZE | TOTAL
| [B] Current Free Space | 225600 | 225600[/B]
Remove | Existing GApps | + 1796 | 227396
Remove | Obsolete Files | + 24 | 227420
Remove | packageinstallerstock | + 2148 | 229568
Install | Core | - 89872 | 139696
Install | calsync | - 1808 | 137888
Install | dialerframework | - 24 | 137864
Install | facedetect | - 540 | 137324
Install | faceunlock | - 14012 | 123312
Install | googletts | - 25520 | 97792
Install | packageinstallergoogle | - 2056 | 95736
Install | search | - 49444 | 46292
Install | speech | - 39604 | 6688
| Buffer Space | - 9216 | -2528
------------------------------------------------------------------
[B]Additional Space Required | 2528[/B]
------------------------------------------------------------------

# End GApps Size Calculations

# Begin User's gapps-config

# End User's gapps-config